The present invention relates generally to apparatus for detecting and surveying the character of a roadbed including the surface on which vehicular traffic passes, such a railway tracks or specially implemented roadways with respect to factors such as rail discontinuities. More specifically, the invention relates to the measurement and detection of rail opening/separation conditions, rail-end mismatch conditions and rail-end batter conditions.
American railroad trains are able to operate over all rail lines in the United States, Canada and Mexico. This is made possible by uniformity of physical dimensions of railroad tracks, switching and control circuits and uniformity of railroad operating rules from railroad to railroad. The uniformity of physical dimensions includes the track dimensions of gage, elevation, surface, alignment, curvature, warp and runoff as well as rail-end mismatch of rail section to rail section, rail-end batter and steel rail. Standards have been established and adopted by the railroads themselves, the Association of American Railroads and the Federal Railroad Administration for the safety of people and rail cars operating over railroad lines.
In the past, a variety of types of apparatus have been proposed for use in determining the profile, alignment, elevation, track gage, curvature, and other parameters or geometry characteristics of a railway track. This is necessary to provide information to a central authority, such as a traffic safety group, for determining points at which rail conditions or track conditions are faulty, require correction and/or for ascertaining the quality of the ride to be expected by passengers on the vehicle.
Currently, one method of track inspection is performed by track inspectors walking along the track or riding at slow speed in a high-rail vehicle. Such structural flaw or discontinuity inspection allows for only one area of detection to be accomplished. That is, track inspection performed in this manner provides a limited amount of data, excluding such information as concerning loaded geometry measurements. This type of inspection reveals some problems such as openings and separations in the rail, rail-end mismatch, and rail-end batter conditions through either the mechanical apparatus or the inspector's careful observations. However, this method has proven to be slow and inefficient for inspection of many miles of track which must be kept in repair to meet safety standards.
Special vehicles have been built capable of measuring track geometry at speeds up to 50 miles per hour using mechanical feelers. See U.S. Pat. No. 3,056,209 to Oliver et al, entitled "Method and Apparatus for Measuring Surface Contours". Other systems operate at speeds up to 150 miles per hour using non-contact electronic sensors (capacitive, magnetic/servo magnetic, photo-optical and laser beam). An example of a capacitive configuration is disclosed in U.S. Pat. No. 3,500,186 to Hronik et al, entitled "Apparatus for High Speed Measurement of Track Geometry".
Apparatus for measuring track geometry, moving at such high speed, has not been able to detect many of the individual rail flaws and discontinuities found by the slower moving vehicle or person employed for that purpose. Apparatus is necessary for receiving a more complete set of data and maintaining safe track conditions. The emphasis on high speed mass transit systems using high speed rail vehicles demands the use of greater speeds in track geometry measurement vehicles to approach actual transportation situations. Such apparatus answering this demand has been disclosed in U.S. Pat. Nos. 3,500,186 and 3,517,307.
The neglected area of consideration in the prior art systems resides in the method of data collection and analysis. Measurement samples taken by the methods of previously described prior art apparatus are recorded only at that point where the signals are sampled. This fails to record any sudden changes in track geometry or rail discontinuity occurring between the sample intervals.
The electrical signals generated by electronic sensor and/or mechanical feeler systems are converted to an electrical analog of each track geometry measurement of interest for the railroad maintenance engineer, and the resultant signal is recorded on a pen and ink recorder for visual analysis. The railroad maintenance engineer studies the recording and decides when a measurement exceeds a safe limit. He manually marks the recording and notes the location of the exception.
More sophisticated prior art systems sample the analog signals at periodic intervals of from 6 inches to several feet then convert these samples to an equivalent digital number and record the sample on digital tape for further analysis after the test run is complete. Highly sophisticated automated systems are capable of processing each sample as it is taken and comparing each sample against preset thresholds to determine if a measurement exceeds a safe limit. A printed message immediately alerts the railroad maintenance engineer of a track condition that needs repair. Systems that digitally sample the analog signals at periodic distances along the track record the measurement of the track only at the point where the sample is taken. Since the point where the measurement sample is taken covers effectively only a small fraction of one inch, and the sampling interval is relatively large (every six inches to several feet), it can be seen that sudden changes in track geometry measurements that occur over short distances (less than the sample interval) can be entirely missed.
Three case conditions can be depicted, as an opening or separation in a track, rail-end mismatch in gage or surface, or a rail-end batter, which might exist and never would be detected and recorded because digital samples were taken on each side of the discontinuity condition. This can obviously be an extremely dangerous oversight.
Accordingly, it is the principal object of this present invention to provide an improved technique for measuring and detecting and recording discontinuities in rail and track conditions.